Development of a relationship between physical parameters of tsunami waves and tsunami intensity based on macroscopic effects and its application to the Italian tsunami database

Tsunamis are rare events. However, their impact can be devastating and it may extend to large geographical areas. For low-probability high-impact events like tsunamis, it is crucial to implement all possible actions to mitigate the risk. The tsunami hazard assessment is the result of a scientific process that integrates traditional geological methods, numerical modelling and the analysis of tsunami sources and historical records. For this reason, analysing past events and understanding how they interacted with the land is the only way to inform tsunami source and propagation models, and quantitatively test forecast models like hazard analyses. The primary objective of this thesis is to establish an explicit relationship between the macroscopic intensity, derived from historical descriptions, and the quantitative physical parameters measuring tsunami waves. This is done first by defining an approximate estimation method based on a simplified 1D physical onshore propagation model to convert the available observations into one reference physical metric. Wave height at the coast was chosen as the reference due to its stability and independence of inland effects. This method was then implemented for a set of well-known past events to build a homogeneous dataset with both macroseismic intensity and wave height. By performing an orthogonal regression, a direct and invertible empirical relationship could be established between the two parameters, accounting for their relevant uncertainties. The target relationship is extensively tested and finally applied to the Italian Tsunami Effect Database (ITED), providing a homogeneous estimation of the wave height for all existing tsunami observations in Italy. This provides the opportunity for meaningful comparison for models and simulations, as well as quantitatively testing tsunami hazard models for the Italian coasts and informing tsunami risk management initiatives.

Synthetic generation of amyloid PET images by non-linear dimensionality reduction inversion

Privacy issues and data scarcity in PET field call for efficient methods to expand datasets via synthetic generation of new data that cannot be traced back to real patients and that are also realistic. In this thesis, machine learning techniques were applied to 1001 amyloid-beta PET images, which had undergone a diagnosis of Alzheimer’s disease: the evaluations were 540 positive, 457 negative and 4 unknown. Isomap algorithm was used as a manifold learning method to reduce the dimensions of the PET dataset; a numerical scale-free interpolation method was applied to invert the dimensionality reduction map. The interpolant was tested on the PET images via LOOCV, where the removed images were compared with the reconstructed ones with the mean SSIM index (MSSIM = 0.76 ± 0.06). The effectiveness of this measure is questioned, since it indicated slightly higher performance for a method of comparison using PCA (MSSIM = 0.79 ± 0.06), which gave clearly poor quality reconstructed images with respect to those recovered by the numerical inverse mapping. Ten synthetic PET images were generated and, after having been mixed with ten originals, were sent to a team of clinicians for the visual assessment of their realism; no significant agreements were found either between clinicians and the true image labels or among the clinicians, meaning that original and synthetic images were indistinguishable. The future perspective of this thesis points to the improvement of the amyloid-beta PET research field by increasing available data, overcoming the constraints of data acquisition and privacy issues. Potential improvements can be achieved via refinements of the manifold learning and the inverse mapping stages during the PET image analysis, by exploring different combinations in the choice of algorithm parameters and by applying other non-linear dimensionality reduction algorithms. A final prospect of this work is the search for new methods to assess image reconstruction quality.

Retinoic acid signaling affects cortical synchrony during sleep.

Delta oscillations, characteristic of the electroencephalogram (EEG) of slow wave sleep, estimate sleep depth and need and are thought to be closely linked to the recovery function of sleep. The cellular mechanisms underlying the generation of delta waves at the cortical and thalamic levels are well documented, but the molecular regulatory mechanisms remain elusive. Here we demonstrate in the mouse that the gene encoding the retinoic acid receptor beta determines the contribution of delta oscillations to the sleep EEG. Thus, retinoic acid signaling, which is involved in the patterning of the brain and dopaminergic pathways, regulates cortical synchrony in the adult.

Lower-stratospheric radiative damping and polar-night jet oscillation events

The effect of stratospheric radiative damping time scales on stratospheric variability and on stratosphere–troposphere coupling is investigated in a simplified global circulation model by modifying the vertical profile of radiative damping in the stratosphere while holding it fixed in the troposphere. Perpetual-January conditions are imposed, with sinusoidal topography of zonal wavenumber 1 or 2. The depth and duration of the simulated sudden stratospheric warmings closely track the lower-stratospheric radiative time scales. Simulations with the most realistic profiles of radiative damping exhibit extended time-scale recoveries analogous to polar-night jet oscillation (PJO) events, which are observed to follow sufficiently deep stratospheric warmings. These events are characterized by weak lower-stratospheric winds and enhanced stability near the tropopause, which persist for up to 3 months following the initial warming. They are obtained with both wave-1 and wave-2 topography. Planetary-scale Eliassen–Palm (EP) fluxes entering the vortex are also suppressed, which is in agreement with observed PJO events. Consistent with previous studies, the tropospheric jets shift equatorward in response to the warmings. The duration of the shift is closely correlated with the period of enhanced stability. The magnitude of the shift in these runs, however, is sensitive only to the zonal wavenumber of the topography. Although the shift is sustained primarily by synoptic-scale eddies, the net effect of the topographic form drag and the planetary-scale fluxes is not negligible; they damp the surface wind response but enhance the vertical shear. The tropospheric response may also reduce the generation of planetary waves, further extending the stratospheric dynamical time scales.

Desenvolvimento de um ressoador retangular de fenda com múltiplas camadas de substrato e com utilização de material PBG para sistema de comunicação sem fio

In the globalized world modern telecommunications have assumed key role within the company, causing a large increase in demand for the wireless technology of communication, which has been happening in recent years have greatly increased the number of applications using this technology. Due to this demand, new materials are developed to enable new control mechanisms and propagation of electromagnetic waves. The research to develop new technologies for wireless communication presents a multidisciplinary study that covers from the new geometries for passive antennas, active up to the development of materials for devices that improve the performance at the frequency range of operation. Recently, planar antennas have attracted interest due to their characteristics and advantages when compared with other types of antennas. In the area of mobile communications the need for antennas of this type has become increasingly used, due to intensive development, which needs to operate in multifrequency antennas and broadband. The microstrip antennas have narrow bandwidth due to the dielectric losses generated by irradiation. Another limitation is the degradation of the radiation pattern due to the generation of surface waves in the substrate. Some techniques have been developed to minimize this limitation of bandwidth, such as the study of type materials PBG - Photonic Band Gap, to form the dielectric material. This work has as main objective the development project of a slot resonator with multiple layers and use the type PBG substrate, which carried out the optimization from the numerical analysis and then designed the device initially proposed for the band electromagnetic spectrum between 3-9 GHz, which basically includes the band S to X. Was used as the dielectric material RT/Duroid 5870 and RT/Duroid 6010.LM where both are laminated ceramic-filled PTFE dielectric constants 2.33 and 10.2, respectively. Through an experimental investigation was conducted an analysis of the simulated versus measured by observing the behavior of the radiation characteristics from the height variation of the dielectric multilayer substrates. We also used the LTT method resonators structures rectangular slot with multiple layers of material photonic PBG in order to obtain the resonance frequency and the entire theory involving the electromagnetic parameters of the structure under consideration. xviii The analysis developed in this work was performed using the method LTT - Transverse Transmission Line, in the field of Fourier transform that uses a component propagating in the y direction (transverse to the real direction of propagation z), thus treating the general equations of the fields electric and magnetic and function. The PBG theory is applied to obtain the relative permittivity of the polarizations for the sep photonic composite substrates material. The results are obtained with the commercial software Ansoft HFSS, used for accurate analysis of the electromagnetic behavior of the planar device under study through the Finite Element Method (FEM). Numerical computational results are presented in graphical form in two and three dimensions, playing in the parameters of return loss, frequency of radiation and radiation diagram, radiation efficiency and surface current for the device under study, and have as substrates, photonic materials and had been simulated in an appropriate computational tool. With respect to the planar device design study are presented in the simulated and measured results that show good agreement with measurements made. These results are mainly in the identification of resonance modes and determining the characteristics of the designed device, such as resonant frequency, return loss and radiation pattern

Antenas planares multicamadas com materiais supercondutores e fotônico para comunicações móveis

Recently, planar antennas have been studied due to their characteristics as well as the advantages that they offers when compared with another types of antennas. In the mobile communications area, the need for this kind of antennas have became each time bigger due to the intense increase of the mobile communications this sector. That needs of antennas which operate in multifrequency and wide bandwidth. The microstrip antennas presents narrow bandwidth due the loss in the dielectric generated by radiation. Another limitation is the radiation pattern degradation due the generation of surface waves in the substrate. In this work some used techniques to minimize the disadvantages (previously mentioned) of the use of microstrip antennas are presented, those are: substrates with PBG material - Photonic Bandgap, multilayer antennas and with stacked patches. The developed analysis in this work used the TTL - Transverse Transmission Line method in the domain of Fourier transform, that uses a component of propagation in the y direction (transverse to the direction real of propagation z), treating the general equations of electric and magnetic field as functions of Ey and Hy. One of the advantages of this method is the simplification of the field equations. therefore the amount of equations lesser must the fields in directions x and z be in function of components Ey and Hy. It will be presented an brief study of the main theories that explain the superconductivity phenomenon. The BCS theory. London Equations and Two Fluids model will be the theories that will give support the application of the superconductors in the microfita antennas. The inclusion of the superconductor patch is made using the resistive complex contour condition. This work has as objective the application of the TTL method to microstrip structures with single and multilayers of rectangular patches, to obtaining the resonance frequency and radiation pattern of each structure

Ressoador retangular defenda com quatro camadas fotônicas

Recently, planar antennas have attracted interest due to its characteristics as well as the advantages they offer compared to other types of antennas. In the area of mobile communications the need for such antennas has become increasingly intense due to development, which requires antennas that operate in multifrequency and broadband. The microstrip antennas have narrow bandwidth due to losses in the dielectric caused by irradiation. Another limitation is the radiation pattern degradation due to generation of surface waves in the substrate. Some techniques are being developed to minimize this bandwidth limitation, as is the case in the study of type materials PBG - Photonic Band Gap, to compose the dielectric material. The analysis developed in this work were performed with use of the method LTT - Transverse Transmission Line, in the field of Fourier transform that uses a component propagating in the y direction (transerve real direction of propagation z), thus treating the general equations of the fields electric and magnetic fields as a functions of y E and Hy . This work has as main objective the method LTT structures resonator line slot with four layers of material photonic PBG, for obtaining the complex resonant frequency and efficiency of this structure. PBG theory is applied to obtain the relative permittivity for the substrate biases sep compounds photonic material. Numerical-computational results in graph form in two dimensions for all the analysis are presented for the proposed structures that have photonic materials, as substrates

Aplicação do método LTT às estruturas retangulares e triangulares em multicamadas e empilhadas em substratos PBG para comunicações móveis

Recently the planar antennas have been studied due to their characteristics as well as the advantages that they offers when compared with another types of antennas. In the mobile communications area, the need for this kind of antennas have became each time bigger due to the intense increase of the mobile communications that needs of antennas which operate in multifrequency and wide bandwidth. The microstrip antennas presents narrow bandwidth due the loss in the dielectric generated by radiation. Another limitation is the radiation pattern degradation due the generation of surface waves in the substrate. In this work some used techniques to minimize the disadvantages (previously mentioned) of the use of microstrip antennas are presented, those are: substrates with PBG material - Photonic Bandgap, multilayer antennas and with stacked patches. The developed analysis in this work used the TTL - Transverse Transmission Line method in the domain of Fourier transform, that uses a component of propagation in the y direction (transverse to the direction real of propagation z), treating the general equations of electric and magnetic field as functions of y and y . This work has as objective the application of the TTL method to microstrip structures with single and multilayers of rectangular and triangular patches, to obtaining the resonance frequency and radiation pattern of each structure. This method is applied for the treatment of the fields in stacked structures. The Homogenization theory will be applied to obtaining the effective permittivity for s and p polarizations of the substrate composed of PBG material. Numerical results for the triangular and rectangular antennas with single layer, multilayers resonators with triangular and rectangular patches are presented (in photonic and isotropic substrates). Conclusions and suggestions for continuity of this work are presented

On two-wavelength Raman fibre laser based on spectral broadening

Raman fibre lasers and converters using the stimulated Raman scattering (SRS) in optical fibre waveguide are attractive for many applications ranging from telecommunications to bio-medical applications [1]. Multiple-wavelength Raman laser sources emitting at two and more wavelengths have been proposed to increase amplification spectrum of Raman fibre amplifiers and to improve noise characteristics [2,3]. Typically, a single fibre waveguide is used in such devices while multi-wavelength generation is achieved by employing corresponding number of fibre Bragg grating (FBG) pairs forming laser resonator. This approach, being rather practical, however, might not provide a good level of cross coherence between radiation generated at different wavelengths due to difference in FBGs and random phase fluctuations between the two wavelengths. In this work we examine a scheme of two-wavelength Raman fibre laser with high-Q cavity based on spectral intracavity broadening [3]. We demonstrate feasibility of such configuration and perform numerical analysis clarifying laser operation using an amplitude propagation equation model that accounts for all key physical effects in nonlinear fibre: dispersion, Kerr nonlinearity, Raman gain, depletion of the Raman pump wave and fibre losses. The key idea behind this scheme is to take advantage of the spectral broadening that occurs in optical fibre at high powers. The effect of spectral broadening leads to effective decrease of the FBGs reflectivity and enables generation of two waves in one-stage Raman laser. The output spectrum in the considered high-Q cavity scheme corresponds to two peaks with 0.2 - 1 nm distance between them. © 2011 IEEE.

Suivi par élastographie ultrasonore après réparation endovasculaire d’anévrisme aorto-iliaque : étude de faisabilité in vivo

Les maladies cardiovasculaires sont la première cause de mortalité dans le monde et les anévrismes de l’aorte abdominale (AAAs) font partie de ce lot déplorable. Un anévrisme est la dilatation d’une artère pouvant conduire à la mort. Une rupture d’AAA s’avère fatale près de 80% du temps. Un moyen de traiter les AAAs est l’insertion d’une endoprothèse (SG) dans l’aorte, communément appelée la réparation endovasculaire (EVAR), afin de réduire la pression exercée par le flux sanguin sur la paroi. L’efficacité de ce traitement est compromise par la survenue d’endofuites (flux sanguins entre la prothèse et le sac anévrismal) pouvant conduire à la rupture de l’anévrisme. Ces flux sanguins peuvent survenir à n’importe quel moment après le traitement EVAR. Une surveillance par tomodensitométrie (CT-scan) annuelle est donc requise, augmentant ainsi le coût du suivi post-EVAR et exposant le patient à la radiation ionisante et aux complications des contrastes iodés. L’endotension est le concept de dilatation de l’anévrisme sans la présence d’une endofuite apparente au CT-scan. Après le traitement EVAR, le sang dans le sac anévrismal coagule pour former un thrombus frais, qui deviendra progressivement un thrombus plus fibreux et plus organisé, donnant lieu à un rétrécissement de l’anévrisme. Il y a très peu de données dans la littérature pour étudier ce processus temporel et la relation entre le thrombus frais et l’endotension. L’étalon d’or du suivi post-EVAR, le CT-scan, ne peut pas détecter la présence de thrombus frais. Il y a donc un besoin d’investir dans une technique sécuritaire et moins coûteuse pour le suivi d’AAAs après EVAR. Une méthode récente, l’élastographie dynamique, mesure l’élasticité des tissus en temps réel. Le principe de cette technique repose sur la génération d’ondes de cisaillement et l’étude de leur propagation afin de remonter aux propriétés mécaniques du milieu étudié. Cette thèse vise l’application de l’élastographie dynamique pour la détection des endofuites ainsi que de la caractérisation mécanique des tissus du sac anévrismal après le traitement EVAR. Ce projet dévoile le potentiel de l’élastographie afin de réduire les dangers de la radiation, de l’utilisation d’agent de contraste ainsi que des coûts du post-EVAR des AAAs. L’élastographie dynamique utilisant le « Shear Wave Imaging » (SWI) est prometteuse. Cette modalité pourrait complémenter l’échographie-Doppler (DUS) déjà utilisée pour le suivi d’examen post-EVAR. Le SWI a le potentiel de fournir des informations sur l’organisation fibreuse du thrombus ainsi que sur la détection d’endofuites. Tout d’abord, le premier objectif de cette thèse consistait à tester le SWI sur des AAAs dans des modèles canins pour la détection d’endofuites et la caractérisation du thrombus. Des SGs furent implantées dans un groupe de 18 chiens avec un anévrisme créé au moyen de la veine jugulaire. 4 anévrismes avaient une endofuite de type I, 13 avaient une endofuite de type II et un anévrisme n’avait pas d’endofuite. Des examens échographiques, DUS et SWI ont été réalisés à l’implantation, puis 1 semaine, 1 mois, 3 mois et 6 mois après le traitement EVAR. Une angiographie, un CT-scan et des coupes macroscopiques ont été produits au sacrifice. Les régions d’endofuites, de thrombus frais et de thrombus organisé furent identifiées et segmentées. Les valeurs de rigidité données par le SWI des différentes régions furent comparées. Celles-ci furent différentes de façon significative (P < 0.001). Également, le SWI a pu détecter la présence d’endofuites où le CT-scan (1) et le DUS (3) ont échoué. Dans la continuité de ces travaux, le deuxième objectif de ce projet fut de caractériser l’évolution du thrombus dans le temps, de même que l’évolution des endofuites après embolisation dans des modèles canins. Dix-huit anévrismes furent créés dans les artères iliaques de neuf modèles canins, suivis d’une endofuite de type I après EVAR. Deux gels embolisants (Chitosan (Chi) ou Chitosan-Sodium-Tetradecyl-Sulfate (Chi-STS)) furent injectés dans le sac anévrismal pour promouvoir la guérison. Des examens échographiques, DUS et SWI ont été effectués à l’implantation et après 1 semaine, 1 mois, 3 mois et 6 mois. Une angiographie, un CT-scan et un examen histologique ont été réalisés au sacrifice afin d’évaluer la présence, le type et la grosseur de l’endofuite. Les valeurs du module d’élasticité des régions d’intérêts ont été identifiées et segmentées sur les données pathologiques. Les régions d’endofuites et de thrombus frais furent différentes de façon significative comparativement aux autres régions (P < 0.001). Les valeurs d’élasticité du thrombus frais à 1 semaine et à 3 mois indiquent que le SWI peut évaluer la maturation du thrombus, de même que caractériser l’évolution et la dégradation des gels embolisants dans le temps. Le SWI a pu détecter des endofuites où le DUS a échoué (2) et, contrairement au CT-scan, détecter la présence de thrombus frais. Finalement, la dernière étape du projet doctoral consistait à appliquer le SWI dans une phase clinique, avec des patients humains ayant déjà un AAA, pour la détection d’endofuite et la caractérisation de l’élasticité des tissus. 25 patients furent sélectionnés pour participer à l’étude. Une comparaison d’imagerie a été produite entre le SWI, le CT-scan et le DUS. Les valeurs de rigidité données par le SWI des différentes régions (endofuite, thrombus) furent identifiées et segmentées. Celles-ci étaient distinctes de façon significative (P < 0.001). Le SWI a détecté 5 endofuites sur 6 (sensibilité de 83.3%) et a eu 6 faux positifs (spécificité de 76%). Le SWI a pu détecter la présence d’endofuites où le CT-scan (2) ainsi que le DUS (2) ont échoué. Il n’y avait pas de différence statistique notable entre la rigidité du thrombus pour un AAA avec endofuite et un AAA sans endofuite. Aucune corrélation n’a pu être établie de façon significative entre les diamètres des AAAs ainsi que leurs variations et l’élasticité du thrombus. Le SWI a le potentiel de détecter les endofuites et caractériser le thrombus selon leurs propriétés mécaniques. Cette technique pourrait être combinée au suivi des AAAs post-EVAR, complémentant ainsi l’imagerie DUS et réduisant le coût et l’exposition à la radiation ionisante et aux agents de contrastes néphrotoxiques.

Suivi par élastographie ultrasonore après réparation endovasculaire d’anévrisme aorto-iliaque : étude de faisabilité in vivo

Les maladies cardiovasculaires sont la première cause de mortalité dans le monde et les anévrismes de l’aorte abdominale (AAAs) font partie de ce lot déplorable. Un anévrisme est la dilatation d’une artère pouvant conduire à la mort. Une rupture d’AAA s’avère fatale près de 80% du temps. Un moyen de traiter les AAAs est l’insertion d’une endoprothèse (SG) dans l’aorte, communément appelée la réparation endovasculaire (EVAR), afin de réduire la pression exercée par le flux sanguin sur la paroi. L’efficacité de ce traitement est compromise par la survenue d’endofuites (flux sanguins entre la prothèse et le sac anévrismal) pouvant conduire à la rupture de l’anévrisme. Ces flux sanguins peuvent survenir à n’importe quel moment après le traitement EVAR. Une surveillance par tomodensitométrie (CT-scan) annuelle est donc requise, augmentant ainsi le coût du suivi post-EVAR et exposant le patient à la radiation ionisante et aux complications des contrastes iodés. L’endotension est le concept de dilatation de l’anévrisme sans la présence d’une endofuite apparente au CT-scan. Après le traitement EVAR, le sang dans le sac anévrismal coagule pour former un thrombus frais, qui deviendra progressivement un thrombus plus fibreux et plus organisé, donnant lieu à un rétrécissement de l’anévrisme. Il y a très peu de données dans la littérature pour étudier ce processus temporel et la relation entre le thrombus frais et l’endotension. L’étalon d’or du suivi post-EVAR, le CT-scan, ne peut pas détecter la présence de thrombus frais. Il y a donc un besoin d’investir dans une technique sécuritaire et moins coûteuse pour le suivi d’AAAs après EVAR. Une méthode récente, l’élastographie dynamique, mesure l’élasticité des tissus en temps réel. Le principe de cette technique repose sur la génération d’ondes de cisaillement et l’étude de leur propagation afin de remonter aux propriétés mécaniques du milieu étudié. Cette thèse vise l’application de l’élastographie dynamique pour la détection des endofuites ainsi que de la caractérisation mécanique des tissus du sac anévrismal après le traitement EVAR. Ce projet dévoile le potentiel de l’élastographie afin de réduire les dangers de la radiation, de l’utilisation d’agent de contraste ainsi que des coûts du post-EVAR des AAAs. L’élastographie dynamique utilisant le « Shear Wave Imaging » (SWI) est prometteuse. Cette modalité pourrait complémenter l’échographie-Doppler (DUS) déjà utilisée pour le suivi d’examen post-EVAR. Le SWI a le potentiel de fournir des informations sur l’organisation fibreuse du thrombus ainsi que sur la détection d’endofuites. Tout d’abord, le premier objectif de cette thèse consistait à tester le SWI sur des AAAs dans des modèles canins pour la détection d’endofuites et la caractérisation du thrombus. Des SGs furent implantées dans un groupe de 18 chiens avec un anévrisme créé au moyen de la veine jugulaire. 4 anévrismes avaient une endofuite de type I, 13 avaient une endofuite de type II et un anévrisme n’avait pas d’endofuite. Des examens échographiques, DUS et SWI ont été réalisés à l’implantation, puis 1 semaine, 1 mois, 3 mois et 6 mois après le traitement EVAR. Une angiographie, un CT-scan et des coupes macroscopiques ont été produits au sacrifice. Les régions d’endofuites, de thrombus frais et de thrombus organisé furent identifiées et segmentées. Les valeurs de rigidité données par le SWI des différentes régions furent comparées. Celles-ci furent différentes de façon significative (P < 0.001). Également, le SWI a pu détecter la présence d’endofuites où le CT-scan (1) et le DUS (3) ont échoué. Dans la continuité de ces travaux, le deuxième objectif de ce projet fut de caractériser l’évolution du thrombus dans le temps, de même que l’évolution des endofuites après embolisation dans des modèles canins. Dix-huit anévrismes furent créés dans les artères iliaques de neuf modèles canins, suivis d’une endofuite de type I après EVAR. Deux gels embolisants (Chitosan (Chi) ou Chitosan-Sodium-Tetradecyl-Sulfate (Chi-STS)) furent injectés dans le sac anévrismal pour promouvoir la guérison. Des examens échographiques, DUS et SWI ont été effectués à l’implantation et après 1 semaine, 1 mois, 3 mois et 6 mois. Une angiographie, un CT-scan et un examen histologique ont été réalisés au sacrifice afin d’évaluer la présence, le type et la grosseur de l’endofuite. Les valeurs du module d’élasticité des régions d’intérêts ont été identifiées et segmentées sur les données pathologiques. Les régions d’endofuites et de thrombus frais furent différentes de façon significative comparativement aux autres régions (P < 0.001). Les valeurs d’élasticité du thrombus frais à 1 semaine et à 3 mois indiquent que le SWI peut évaluer la maturation du thrombus, de même que caractériser l’évolution et la dégradation des gels embolisants dans le temps. Le SWI a pu détecter des endofuites où le DUS a échoué (2) et, contrairement au CT-scan, détecter la présence de thrombus frais. Finalement, la dernière étape du projet doctoral consistait à appliquer le SWI dans une phase clinique, avec des patients humains ayant déjà un AAA, pour la détection d’endofuite et la caractérisation de l’élasticité des tissus. 25 patients furent sélectionnés pour participer à l’étude. Une comparaison d’imagerie a été produite entre le SWI, le CT-scan et le DUS. Les valeurs de rigidité données par le SWI des différentes régions (endofuite, thrombus) furent identifiées et segmentées. Celles-ci étaient distinctes de façon significative (P < 0.001). Le SWI a détecté 5 endofuites sur 6 (sensibilité de 83.3%) et a eu 6 faux positifs (spécificité de 76%). Le SWI a pu détecter la présence d’endofuites où le CT-scan (2) ainsi que le DUS (2) ont échoué. Il n’y avait pas de différence statistique notable entre la rigidité du thrombus pour un AAA avec endofuite et un AAA sans endofuite. Aucune corrélation n’a pu être établie de façon significative entre les diamètres des AAAs ainsi que leurs variations et l’élasticité du thrombus. Le SWI a le potentiel de détecter les endofuites et caractériser le thrombus selon leurs propriétés mécaniques. Cette technique pourrait être combinée au suivi des AAAs post-EVAR, complémentant ainsi l’imagerie DUS et réduisant le coût et l’exposition à la radiation ionisante et aux agents de contrastes néphrotoxiques.

Plantar flexion force induced by amplitude-modulated tendon vibration and associated soleus V/F-waves as an evidence of a centrally-mediated mechanism contributing to extra torque generation in humans

Background: High-frequency trains of electrical stimulation applied over the human muscles can generate forces higher than would be expected by direct activation of motor axons, as evidenced by an unexpected relation between the stimuli and the evoked contractions, originating what has been called “extra forces”. This phenomenon has been thought to reflect nonlinear input/output neural properties such as plateau potential activation in motoneurons. However, more recent evidence has indicated that extra forces generated during electrical stimulation are mediated primarily, if not exclusively, by an intrinsic muscle property, and not from a central mechanism as previously thought. Given the inherent differences between electrical and vibratory stimuli, this study aimed to investigate: (a) whether the generation of vibration-induced muscle forces results in an unexpected relation between the stimuli and the evoked contractions (i.e. extra forces generation) and (b) whether these extra forces are accompanied by signs of a centrally-mediated mechanism or whether intrinsic muscle properties are the redominant mechanisms. Methods: Six subjects had their Achilles tendon stimulated by 100 Hz vibratory stimuli that linearly increased in amplitude (with a peak-to-peak displacement varying from 0 to 5 mm) for 10 seconds and then linearly decreased to zero for the next 10 seconds. As a measure of motoneuron excitability taken at different times during the vibratory stimulation, short-latency compound muscle action potentials (V/F-waves) were recorded in the soleus muscle in response to supramaximal nerve stimulation. Results: Plantar flexion torque and soleus V/F-wave amplitudes were increased in the second half of the stimulation in comparison with the first half. Conclusion: The present findings provide evidence that vibratory stimuli may trigger a centrally-mediated mechanism that contributes to the generation of extra torques. The vibration-induced increased motoneuron excitability (leading to increased torque generation) presumably activates spinal motoneurons following the size principle, which is a desirable feature for stimulation paradigms involved in rehabilitation programs and exercise training.

Emulation of an OWC Ocean Energy Plant With PMSG and Irregular Wave Model

Ocean energy is a promising resource for renewable electricity generation that presents many advantages, such as being more predictable than wind energy, but also some disadvantages such as large and slow amplitude variations in the generated power. This paper presents a hardware-in-the-loop prototype that allows the study of the electric power profile generated by a wave power plant based on the oscillating water column (OWC) principle. In particular, it facilitates the development of new solutions to improve the intermittent profile of the power fed into the grid or the test of the OWC behavior when facing a voltage dip. Also, to obtain a more realistic model behavior, statistical models of real waves have been implemented.

Rogue waves generation via nonlinear soliton collision in multiple-soliton state of a mode-locked fiber laser

We report for the first time, rogue waves generation in a mode-locked fiber laser that worked in multiple-soliton state in which hundreds of solitons occupied the whole laser cavity. Using real-time spatio-temporal intensity dynamics measurements, it is unveiled that nonlinear soliton collision accounts for the formation of rogue waves in this laser state. The nature of interactions between solitons are also discussed. Our observation may suggest similar formation mechanisms of rogue waves in other systems.